A U.S. court has called for a recalculation of sums underlying duties slapped last year on imports of steel pipes for the energy sector from South Korea, in a setback for domestic producers.

The U.S. Court of International Trade ruled that the Department of Commerce should reconsider its calculation of profit, a key input in determining the level of duties. The ruling was dated Sept. 2.

The Commerce Department and the U.S. International Trade Commission last year backed a complaint by U.S.-based steel companies, including United States Steel Corp, Tenaris SA subsidiary Maverick Tube Corporation, JMC Steel Group Inc's Energex Tube, Russia's TMK IPSCO and France's Vallourec Star, against imports of "oil country tubular goods" (OCTG).

South Korea was the biggest producer targeted in the case, which also covered imports from India, Taiwan, Turkey, Ukraine and Vietnam.

The Commerce Department set duties on imports from South Korea's Hyundai Hysco at 15.75 percent, those from Nexteel at 9.89 percent and all other South Korean producers at 12.82 percent. The companies argued the duties were too high.

"Commerce's Final Determination is remanded in part ... for it to reconsider its calculation," the U.S. Court of International Trade said, although it upheld other parts of the decision. The Commerce Department had no comment on the ruling.

A spokesman for the Steel Manufacturers Association, which represents a number of North American steelmakers, said the ruling was disappointing but only one step in ongoing litigation.

"South Korea is a critical part of the case due to the tonnage involved and the potential for further harm to an already challenged market," the spokesman said.

"We remain optimistic that the final decision will adequately address the harm that has been done to domestic steel producers, their employees, and their surrounding communities."

The U.S. companies said OCTG imports sold cheaply and using government subsidies had harmed their business, dragged prices down and triggered job cuts.